D&D 5E Proficiency bonus based AC and armor as temp HP with reduced AC bonus?

[Crimson Longinus]

I was recently contemplating the same issue due a low-tech setting. This was my solution.

 

[Quartz]

What incentive (if any) would the guy in plate armor have for wearing it?

Pick one: because you would be denied your PB when you would be denied your Dex bonus, or it fits the image (cf. Hollywood Heroics).

Note that at low levels Plate is strictly better, giving a base AC of 18 rather than 12+3 = 15.

 

[DND_Reborn]

Pick one: because you would be denied your PB when you would be denied your Dex bonus, or it fits the image (cf. Hollywood Heroics).

Note that at low levels Plate is strictly better, giving a base AC of 18 rather than 12+3 = 15.

Very true, but think about it: you buy armor to protect you, but then when you are hero of the realm you don't need it anymore and put on a suit of studded leather. AC is the same, but now your skill is so good you doesn't need the heavy armor (despite wearing it for dozens of adventures and it saving your life over and over again). There's no incentive to continue wearing the armor that you've been using.

So, why wouldn't you get better at wearing the armor you've been wearing for a long time?

I certainly don't think there is anything wrong with the idea, our own house-rule grants players an AC bonus (+1 at tier 2, +2 at tier 3, and +3 at tier 4). I just wonder why only players in lighter armors can benefit from their skill?

I would consider something like this:

 

[Kobold Avenger]

I think 8 or some other base number + proficiency bonus might be the preferable option over doing things like dividing proficiency bonus, or proficiency bonus but no greater than x.

The base number could very by class, like the ones better at fighting getting a higher base number. I know others have many problems with the Monk, but generally Fighter and Monk should have a similar AC/Defense.

 

[Quartz]

I would consider something like this:

I think that fails the KISS principle.

 

[DND_Reborn]

I think that fails the KISS principle.

The +1 per tier is simple of course, but doesn't help light and medium armor wearers like the OP was trying to do.

Anyway, I don't think it is really that complex. It is just proficiency bonus for light armors, proficiency bonus -2 for medium, and heavy armors half proficiency (round down) -1.

 

[Xeviat]

Lets imagine, for a moment, we were trying to make AC scale like Attack does. Attack scales with proficiency, and if you're starting with a 16 in your attack stat, an additional +2. So you're gaining +6 over your career.

Armor scales at +2 currently; heavy armor wearers upgrade from chainmail to splint to plate. Light armor wearers, at least Rogues and the like, are likely starting with 16 Dex and studded leather (at least rather quickly, since it costs less than chainshirt, scalemail, or chainmail). They're going to get +2 to their Dex mod from ASIs.

So, AC currently, doesn't scale much. Now, there are more items that grant AC bonuses than there are items that grant attack bonuses, so maybe that was the intent. But, the Monk's AC can scale by +5, if they start with Dex 16 and Wis 14 (which gives them equivalent AC as Studded Leather and Dex 16) from their ASIs, and they get access to many of the same AC boosting items (just no shields and armor).

Having the AC calculation be changed to 8+Prof+Dex, and then adjusting the armors, could work. It would be an AC boost, though, so you might want to adjust some of the magic AC boosting items (like ring of protection, magic shields, and the like).

I'd be wary of having medium and heavy armor wearers have a lower defense score (which is what I'd call it if you were taking away armor granting an AC bonus, and switching it for armor HP or damage reduction).